Blade angle checking apparatus



June 25, 1957 B. F. JORDAN ET AL BLADE ANGLE CHECKING APPARATUS 5 Sheets-Sheet 1 LP Y L IN V EN TORS. F. JUEDHN JOHN W. PLf/IJHNT June 25, 1957 B. F. JORDAN ETAL 2,796,669

BLADE ANGLE CHECKING APPARATUS Filed Oct. 50, 1953 5 Shegts-Sheet 2 55.5 1W 3 XL 1 HTTOENEX? June 25, 1957 F, JORDAN HAL I 2,796,669

BLADE ANGLE CHECKING APPARATUS Filed Oct. 30, 1953 5 Sheets-Sheet 3 Ll BY L g 9 irram/zr United States Patent BLADE ANGLE CMCKING APPARATUS Benjamin Franklin Jordan and John Wright lleasant, San Antonio, Tex.

Application October 30, 1953, Serial No. 339,597

9 Claims. (Cl. 33-174) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to us of any royalty thereon.

This invention relates to apparatus for checking propeller blade angle of a blade assembly prior to its incorporation in a hub to form a propeller assembly. The usual method of checking propeller blade angle prior to this invention was by checking the blades with a protractor at prescribed stations after assembly to form a propeller. In such prior method of checking propeller blade angle, in the event of incorrect blade angle, the blade assembly in error had to be completely removed, adjusted, reassembled and then checked again after assembly in the propeller. This process of assembly and disassembly of a blade from a propeller is a tedious and time consuming operation and this trial and error method previously utilized is expensive both in man hours and economy. The present invention enables the quick accurate check of blade angle prior to the assembly of the blade in a propeller hub whereby the tedious and time consuming operation of assembly and disassembly due to blade angle errors is eliminated. The invention in the form presented herein is particularly directed to variable pitch propeller blade assemblies such as employed in Curtiss and Hamilton Standard propellers. But while directed to such propeller blade assemblies the apparatus may readily be adapted to a variety of propeller blade assemblies of a similar nature by means of mere mechanical adaptations within the skill of a mechanic versed in the art.

The invention apparatus in the practical form disclosed herein comprises a blade angle indicator assembly adapted to be mounted in engagement with a segmental gear assembly of a variable pitch propeller blade assembly in predetermined fashion with a bar so related to the indicator assembly, when in mesh with the segmental gear assembly in the predetermined manner, as to define the blade angle at the check station when the blade assembly is placed on two V blocks on a surface plate with one V block located approximately 6 inches fiom the butt end while the other V block is placed at the prescribed check station of the blade which is usually at the 72 inch station, the second V block being slotted for a blade template to lay across the top for the face of the blade to rest upon. By means of such apparatus each blade assembly on being placed on the V blocks as prescribed may be checked and corrected for proper blade angle prior to assembly into a propeller.

An object of this invention is to provide an improved apparatus for checking propeller blade angle.

A further object of the invention is to provide a novel blade angle indicator unit adaptable to indicate true blade angle at a check station prior to assembly of a blade in a propeller.

Another object of the invention is to provide blade angle checking apparatus which is simple and positive in operation and eflective to eliminate tedious and time consuming trial and error methods of checking blade angle of a blade to be used in a variable pitch propeller.

An additional object of the invention is to provide a blade angle checking apparatus employing an indicator whereby the true blade angle at a prescribed check station may be accurately and quickly made available.

Other objects and advantages of this invention will be readily apparent to those versed in the art from the following description taken in conjunction with the accompanying drawings wherein:

Fig. 1 shows the side view of the propeller blade assembly in test position with the novel blade angle indicator assembly applied;

Fig. 2 is a front view of the novel blade angle indicator assembly;

Fig. 3 is a cross-sectional view of the blade angle indicator assembly taken on line 3--3 of Fig. 2 eliminat ing the counterweight arm for clarity of detail;

Fig. 4 is a top view of the novel blade angle indicator assembly;

Fig. 5 is a partial sectional view taken on line 5-5 of Fig. 2;

Fig. 6 is a sectional view taken on line 6-6 of Fig. 4;

Fig. 7 is a detail showing of the gear segment.

Fig. 8 is an exploded, perspective view of interfitting parts at the butt end of a variable pitch propeller blade and including a segmental gear assembly.

Fig. 9 is a front view of the testing apparatus in posi tion for testing a blade.

As shown in Figs. 1 and 9 in the employment of the invention apparatus, a stand 1 is arranged with a top surface plate or table top 2. The propeller blades to be tested are those for use with variable pitch type propeller. Each such blade has, at its butt end, a segmental ear assembly A which includes a driven gear element 24 formed with a bevel gear segment 24a. The hub of element 24 has external splines 24b and is insertable into a ring element 25 which is provided internally with splines 25a to mate with splines 24b. Element 25 has a reduced rear portion with external splines 25b. The rear portion of element 25 fits into a collar 26 internally formed with mating splines 26a for the splines 25b. Collar 26 is rigid with the butt end collar 27 of the propeller blade assembly. A cuff 28 is attached through yokes 29 to the collar 27. When the blade assembly, including the blade proper and the parts 24 to 29, are assembled with other blades in the propeller hub (not shown), a servo gear (not shown) meshes with a segmental gear 240 on each blade assembly so that rotative adjustment of the servo gear will vary the pitch of the blades. All the blades proper in such propeller assembly are initially required to be at a predetermined blade angle relative to their respective segmental gears 24a. The blade angle can be adjusted by removing ring element 25 from collar 26 and then reinserting it in a diflerent rotative position. Further adjustment is provided for by removing gear 24 from 25 and reinserting it in a diiferent relative rotative position. A propeller blade assembly 3 of this type to be tested for blade angle is arranged with its butt end collar 27 resting in a V block 4 approximately six inches from its end, the V block resting on and suitably secured to the surface plate 2. A V block 5 on the surface plate is slotted to receive a blade template 6 on which the blade face rests at its prescribed check station which is usually the 72 inch station. p

The segmental gear assembly A has previously been inserted in the splines of the propeller blade collar 27 in an initial basic angularly indexed position.

The novel blade angle indicator assembly comprises an adapter plate 7 having a central aperture and a lug 8 extending from the periphery thereof to which is integrally fixed a gear segment 9 extending at an angle from a face of the lug. The lug to the rear of the gear segment hastwo threaded holes 3a therein. To the rear of the adapter plate 7 is bolted a circular cup element 10 with a conical recess therein to accommodate the butt end of a segmental gear assembly. To the front face of the adapter plate is bolted a blade angle indicator arm element 11 which has arcuate slots 12 concentric with the central aperture in adapter plate 7 and the axial center of gear segment 9 fixed to the plate 7. Bolts 32 extend through the slots 12 and the adapter plate 7 and are threaded into the cup 10 to provide a secure assembly as shown in Fig. 3. The element 11 has a central disklike portion, which is formed with the arcuate slots 12, and has a pair of diametrically opposite arms or bar ex tensions 13. Aligned on the center line of the bar ex tensions 13 of the element 11' are contact elements 14 extending through an insulator 15 at either end of the bar and being threaded to receive a nut with a washer to secure the contact members to the bar. It is evident that the angular position of the element 11 and its extensions 13 with respect to the gear segment 9 may be adjusted after loosening bolts 32. The bolts may then be tightened to clamp the element 11 in its new position. Bolted to the lug 8 on the adapter plate 7 by means of bolts 33 threaded into the hole 8a is an offset counterweight arm 16 having a notched portion 17 near the outer end thereof to receive a weight W thereon.

In the assembly of the blade angle indicator unit it is secured by a central stud 18 to the segmental gear assembly A on the. propeller blade and, for Hamilton propeller blades, the center tooth of the gear segment 9 is set in the center of the segmental gear such as 24a (Fig. 8) thereon Whereas in Curtiss propeller blades, the setting is made with an indexed tooth on the segmental gear of the blade assembly in mesh with the center tooth of the gear segment 9 on the blade angle indicator assembly.

A master blade assembly known to be correct as to blade angle is employed to set the elements 9 and 13 in the proper angular relation to provide an accurate gage or standard for determination of true blade angle. Accordingly with such master blade assembly in test position on the table top 2, the center gear tooth on the gear segment 9 integral with the adapter plate 7 is meshed with the segmental gear tooth prescribed for the particular blade assembly as referred to previously herein with the cup section 10 receiving any protrusion from the segmental gear assembly. Then the indicator arm unit 11 including arms 13 is connected to the adapter plate loosened sufiiciently to enable it to be angularly adjusted relative to the plate 7. A standard propeller blade protractor P with its arm 35 set at the required blade angle, as indicated by the scale parts 36 and 37, is supported on table top- 2 in front of the testing apparatus. The protractor is shifted along the table top to position its arm 35 over the contact studs 14 on arms 13. The unit 11, with arms 13, is then angularly adjusted to engage the contact studs simultaneously withthe underside of arm 35. The arms 13 are then at the same angle as the protractor arm 35 relative to the gear segment 9. This is the required blade angle testing position of the arms 13. Protractor arm 35 is of conductive metal and when simultaneously engaged by contact studs 14 on the arms 13 completes a circuit through a signal unit C. The signal unit may be of the visual or audible type or of any other known type and when it operates indicates that the arms 13 are at the same angle as the protractor arm 35. With arms 13 set at the required testing angle, the bolts 32 are tightened to fix the arms in position relative to plate 7 and the gear segment'9 fixed to lug 8 of the plate 7. Note may be taken of the fact that arm 16 when loaded by a weight W serves to take up backlash between the gear segment 9 and the segmental gear 24a of the blade assembly with which the segment 9 is meshed when the blade assembly is under test,

With arms 13 set at the required blade checking angle by the above procedure, the blade angle testing apparatus is ready to check blade assemblies of the described type for blade angle. In effect, the testing apparatus, having been set under control of a master blade assembly, is ready to compare other blade assemblies of the same type with the master blade assembly.

The manner of utilizing the apparatus of the invention is to set up the propeller blade assembly 3 to be checked on the V blocks 4 and 5 on the stand 1 in the manner prescribed herein with the block 4 six inches from the butt end and block 5 at the check station. Then the blade angle indicator assembly with the elements secured together is secured to the segmental gear assembly by means of the stud 18 centrally thereof with the gear segment 9 of the adapter element 7 having itscentral tooth, in the case of a Curtiss propeller blade, for example, aligned with the indexed tooth on the segmental gear in mesh therewith, or as prescribed in the case of a Hamilton blade assembly with the center tooth of the gear segment in the center of the segmental gear in mesh therewith. A weight W is then hung on the ofiset arm 16 to take out any backlash in the gears. The standard blade protractor P is then employed setting on the surface plate 2 adjacent the butt'end of the blade. The protractor arm '35 is then adjusted until it contacts the right hand contact stu'd 14 on the right hand arm 13 and then the p'rotractor is moved until the arm 35 also contacts the left hand contact stud 14 on the left hand arm 13. When protractor arm 35 is bridging both contact studs 14, it completes the circuit of signal unit C. The protractor angle is then read and if it is within an allowance tolerance from the required blade angle, the angle assembly under test is passed as having the proper blade angle. If the test shows the blade angle to be outside the tolerable limit, the blade assembly is removed from testing position and its segmental gear 24a is rotatively readjusted relative to the blade proper in the manner now understood. The readjusted blade assembly can then be quickly re-checked.

As can be readily seen all test assembly and disassembly of a propeller blade assembly is avoided eliminating a substantial amount of Work and saving a substantial amount of time due to the difiiculty of assembling and disassembling a propeller assembly.

While a single practical embodiment of the invention is shown herein, other modifications and applications thereof will be readily apparent'to those versed in the art and such lies within the scope of the invention which is \defined by the scope of the claims herewith.

What is claimed is: i

1. Blade angle testing apparatus for a propeller blade assembly of the type having a segmental gear at the butt end having an indexing tooth and the blade angle of which is the angular relation, about the axis of the segmental gear, between the indexing tooth of the segmental gear and a given check section of the blade proper; said testing apparatus comprising a structure to support such blade as sembly in a test position, a test unit having an axial center and fixable in facing position relative to the segmental gear or" the assembly and in coaxial alinement with the said segmental gear, a toothed element provided on the test unit on a predetermined line radially disposed to axial center of the unit and said toothed element being meshed with said indexing tooth of the segmental gear when the unit is fixed in its said position relative to the blade assembly, a pair of electrical contact elements provided on the test unit along a straight line at a predetermined angle relative to a predetermined radial disposition of the toothed element corresponding to the correct blade angle, and electrical means controlled by said pair of electrical contact elements according to whether the angle made .by said straight line relative to the segmental gear of the blade assembly, While the toothed element is in mesh with the indexing tooth, corresponds to said correct blade angle.

,2. Blade angle testing apparatus for a propeller blade assembly of the type having a segmental gear at its butt end and the blade angle of which is the angular relation, about the axis of the segmental gear between the segmental gear position and a check section of the blade proper; said testing apparatus comprising a structure to support such blade assembly in a test position, a test unit having an axial center and fixable in facing position relative to the segmental gear with said axial center in line with the axis of the segmental gear, a toothed element on the test unit in radial disposition relative to said axial center and meshed with a predetermined tooth of the :segmental gear of the blade assembly when the test unit is fixed in said facing position, means disposed on said unit along a substantially diametral line at such angle relative to the radial disposition of the toothed element as to cor-responnd to the correct blade angle, and means, including a protractor coacting with said means disposed on the unit, for determining Whether the latter means is at an angle to the segmental gear equal to the correct blade angle while said toothed element is in mesh with said predetermined tooth of the segmental gear.

3. Blade angle testing apparatus for a variable pitch propeller blade assembly of the type having a driven gear at the butt end and the blade angle of which is the angular relation about the gear axis between a. predetermined tooth of the gear and a transverse section of the blade proper at a predetermined distance from the butt end; said testing apparatus comprising a structure including a surface plate and means to support the blade assembly in a test position on said surface plate, a test unit having an axial center and settable in coaxial facing position relative to said gear, a toothed element on the test unit meshed with said predetermined tooth of the gear when the test unit is set in said facing position, linearly disposed means on the test unit such that with the toothed element meshed with said predetermined tooth of said gear the latter means makes an angle relative to the surface plate corresponding to the actual blade angle of the blade assembly under test, and protractor means carried by said surface plate for coacting with the linearly disposed means for comparing said actual blade angle with the required correct blade angle.

4. Apparatus as in claim 3, said means coacting with the linearly disposed means including a protractor unit supported on the surface plate.

5. Apparatus as in claim 3, said means coacting with the linearly disposed means including an electric signal device.

6. Apparatus as in claim 3, said linearly disposed means including spaced contacts and said means coacting with the linearly disposed means including a protractor unit or the surface plate with a conductive protractor arm to bridge said contacts and further including a signal device operated upon protractor arm bridging said contacts.

7. Apparatus as in claim 3, said test unit including a mounting plate and a member provided With saidlinearly disposed means and arranged on said mounting plate for arcuate adjustment about said axial center to enable the linearly dis-posed means to be set at diiferent check angles relative to the toothed element on the test unit.

8. Apparatus as in claim 7, said member having a pair of alined arms at opposite sides of the axial center of the test unit and said linearly disposed means including elements on the respective arms.

9. Apparatus as in claim 3, said test unit including means to take up back lash between said toothed element and said gear on the blade assembly.

References Cited in the file of this patent UNITED STATES PATENTS 1,736,247 Bodenlos Nov. 19, 1929 2,096,752 Metcallf Oct. 26, 1937 2,132,407 Fowler Oct. 11, 1938 

